+//________________________________________________________
+Int_t AliITSVertexer3D::Prepare3DVertexPbPb(){
+ // Finds the 3D vertex information in Pb-Pb events using tracklets
+ AliDebug(1,"High multiplicity event.\n");
+
+ Int_t nxy=(Int_t)(2.*fCoarseMaxRCut/f3DBinSize);
+ Double_t xymi= -nxy*f3DBinSize/2.;
+ Double_t xyma= nxy*f3DBinSize/2.;
+ Int_t nz=(Int_t)(2.*fZCutDiamond/f3DBinSize);
+ Double_t zmi=-nz*f3DBinSize/2.;
+ Double_t zma=nz*f3DBinSize/2.;
+ Int_t nolines=fLines.GetEntriesFast();
+ TH3F *h3dv = new TH3F("h3dv","3d tracklets",nxy,xymi,xyma,nxy,xymi,xyma,nz,zmi,zma);
+
+ for(Int_t itra=0; itra<nolines; itra++){
+ Double_t wei = GetFraction(itra);
+ //printf("tracklet %d ) - weight %f \n",itra,wei);
+ if(wei>1.e-6){
+ AliStrLine *str=(AliStrLine*)fLines.At(itra);
+ Double_t t1,t2;
+ if(str->GetParamAtRadius(fCoarseMaxRCut,t1,t2)){
+ do{
+ Double_t punt[3];
+ str->ComputePointAtT(t1,punt);
+ h3dv->Fill(punt[0],punt[1],punt[2],wei);
+ t1+=f3DBinSize/3.;
+ } while(t1<t2);
+ }
+ }
+ }
+ Int_t noftrk,noftim;
+ FindPeaks(h3dv,f3DPeak,noftrk,noftim); // arg: histo3d, peak, # of contrib., # of other peak with same magnitude
+
+
+ // Remove all the tracklets which are not passing near peak
+
+ while(nolines--){
+ AliStrLine *str=(AliStrLine*)fLines.At(nolines);
+ Double_t dist = str->GetDistFromPoint(f3DPeak);
+ if(dist>(2.*f3DBinSize)) fLines.RemoveAt(nolines);
+ }
+ fLines.Compress();
+ nolines=fLines.GetEntriesFast();
+
+ delete h3dv;
+
+ Int_t *validate2 = new Int_t [fLines.GetEntriesFast()];
+ for(Int_t i=0; i<fLines.GetEntriesFast();i++) validate2[i]=1;
+ for(Int_t i=0; i<fLines.GetEntriesFast();i++){
+ if(validate2[i]==0) continue;
+ AliStrLine *l1 = (AliStrLine*)fLines.At(i);
+ if(l1->GetDistFromPoint(f3DPeak)> fDCAcut)fLines.RemoveAt(i);
+ for(Int_t j=i+1; j<fLines.GetEntriesFast();j++){
+ AliStrLine *l2 = (AliStrLine*)fLines.At(j);
+ if(l1->GetDCA(l2)<0.00001){
+ Int_t delta1=(Int_t)l1->GetIdPoint(0)-(Int_t)l2->GetIdPoint(0);
+ Int_t delta2=(Int_t)l1->GetIdPoint(1)-(Int_t)l2->GetIdPoint(1);
+ Int_t deltamod1=(Int_t)l1->GetIdPoint(0)/kMaxCluPerMod
+ -(Int_t)l2->GetIdPoint(0)/kMaxCluPerMod;
+ Int_t deltamod2=(Int_t)l1->GetIdPoint(1)/kMaxCluPerMod
+ -(Int_t)l2->GetIdPoint(1)/kMaxCluPerMod;
+ // remove tracklets sharing a point
+ if( (delta1==0 && deltamod2==0) ||
+ (delta2==0 && deltamod1==0) ) validate2[j]=0;
+
+ }
+ }
+ }
+ for(Int_t i=0; i<fLines.GetEntriesFast();i++){
+ if(validate2[i]==0) fLines.RemoveAt(i);
+ }
+
+ delete [] validate2;
+ fLines.Compress();
+
+
+ AliDebug(1,Form("Number of tracklets (after 3rd compression) %d",fLines.GetEntriesFast()));
+
+ fVert3D=AliVertexerTracks::TrackletVertexFinder(&fLines,0);
+ fVert3D.GetXYZ(f3DPeak);
+
+ return 0;
+}
+